There is a general need for dental appliances that can be specifically tailored to an individual patient, that can be fabricated within a short time during a single patient visit and that are durable and comfortable to use even after repeated insertion and removal from the oral cavity. A number of appliances are in current use in dentistry, but none provide the combination of characteristics described above. For example, commercially available night guards are designed to be worn while sleeping. The guards mitigate the effects of involuntary grinding on the teeth and the associated oral tissues and structures. In addition, the guards provide relief in some patients from headaches and jaw pain that result from teeth grinding. Generally, these devices consist of a low glass transition thermoplastic elastomer that is contained within a molded thermoplastic tray. The tray may be rigid or flexible but should have a higher glass transition temperature than the thermoplastic elastomer that it holds. The patient places this appliance briefly in boiling water and then inserts it into the mouth, biting down to impress and conform the thermoplastic elastomer to the teeth. On cooling, the impression is preserved.
The results obtained using such technology leave much to be desired. First, insertion of a hot device into the mouth always carries considerable risk of injury. Second, the results and utility of the appliance depend on upon many variables including how well the patient positions the device and how much pressure is applied during the bite down portion of the process. Further, the flow of the thermoplastic material during the above process is very limited, such that only portions of the teeth are encapsulated; this results in a loose and ill-fitting appliance. These negative factors result in poor patient use compliance and a corresponding unsatisfactory relief of the symptoms of teeth grinding. Considerably more expensive but better fitting night guards can be fabricated by an impression-casting process as described below for sporting mouth guards.
Two methods are used in the fabrication of mouth guards used to protect teeth during spotting or other activities. They can be made by the so-called “boil and bite” process described above for night guards. In addition, these guards can be fabricated by taking a dental impression by licensed dental personnel, followed by making a cast model from the impression and then forming the final mouth guard around this casting. This normally requires two visits by the patient to a dental office as well as several days for completion of the entire process. Further, the long, complicated, multistep process required for the fabrication adds significantly to the overall cost of the resulting appliance. There are some modifications of this technique whereby sports mouth guards are made by having the athlete take his own impression and then fabricating the mouth guard in a laboratory. This reduces the cost somewhat. A greatly simplified one-step, rapid, low cost process would be highly desirable.
Bleaching agents are commonly used to whiten teeth. To afford an even, cosmetically attractive whitening process over all the targeted teeth, it is desirable to find some method in which the bleaching agent can be applied uniformly. During the bleaching process, it would be advantageous to isolate the teeth undergoing whitening within the oral cavity since the process may require several minutes to several hours for completion. In such instances, it is further desirable to limit the potential ingestion of bleaching agents by the patient as well as the exposure of dental tissues to these agents. In some cases, the bleaching agents are applied to the teeth and, thereafter, the bleaching action is aided by the exposure to UV light.
Periodontal disease, popularly called gingivitis, is present to varying degrees in approximately 85% of the population. In severe cases this bacterial disease results in serious infections of the gums with accompanying soreness and bleeding and may eventually lead to erosion of the teeth below the gum line and their subsequent loss. Treatments for periodontal disease include antibacterial agents that kill bacteria responsible for periodontal disease on contact and oxidizing agents that remove the protective bacterial biofilm formed on teeth and gums that promotes bacterial reinfection. The devices of this invention can be employed in two ways to mitigate the effects of periodontal disease. Custom fit trays can be readily, quickly and inexpensively constructed using the technology described herein. These trays can be filled with antibacterial and/or oxidizing agents.
Certain common requirements are necessary to successfully address all of the above targeted dental appliances and other applications. First, the materials employed must possess no appreciable oral or dermal toxicity. They should be odorless and tasteless and should provide no permanent bonding to oral tissues or teeth. They should release easily and cleanly from those tissues and teeth to preserve fine details and fit of the dental appliance. The materials should be compatible with water and saliva as well as other agents commonly found in oral fluids and should undergo no appreciable degradation in the presence of those agents. Silicones, poly(dimethylsiloxanes), possess all of these properties and are, therefore, the favored materials of choice for such applications. However, commercially available crosslinkable silicones currently used in dentistry, specifically in dental impressions, are not suitable for the above applications since they both have unacceptably long cure times and possess poor mechanical properties, especially poor tear strength. For the above described applications, it is desirable to have cure times under fifteen minutes and, ideally, under seven minutes at physiological temperatures (approx. 37° C.) and high tear strengths that allow repeated removal and reinsertion of the dental appliance. In addition, the silicone elastomer produced should be tough and possess sufficient stiffness to resist bite-through by the patient while at the same time being soft and compliant for comfortable long-term wear. Prior to cure, the silicone should possess a sufficiently high viscosity so that the resin does not flow appreciably during application and cure.
Currently, the above described requirements are not met by any existing material, silicone or otherwise. It is also recognized that a crosslinkable silicone material by itself is not usually sufficient for the fabrication of a workable dental appliance. Commonly, the device will consist of a combination of a crosslinkable silicone together with a silicone curing tray that becomes an integral portion of the resulting finished dental appliance.